As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.
High current information handling system loads, such as for CPU's and memory, typically require multi-phase voltage regulators (VR's). A power stage phase of each VR phase is usually composed of a MOSFET (metal oxide semiconductor field effect transistor) driver, a high-side MOSFET, a low-side MOSFET and an inductor with all the phase inductors being tied together at their output. One example of such a multi-phase VR architecture may be found in U.S. Pat. No. 7,999,520. Because the multiple power phases of such a multi-phase VR are tied together, it makes identification of an individual bad power phase (or phase) difficult, as the failure could be occurring on any one or more of the power phases. As used herein, a bad power phase is defined as a non-working power phase that is incapable of delivering power from input to the output. Such a bad power phase may be caused, for example, by poor soldering (open or short circuit) or a bad/missing component. Thus, if one of the individual power phases is not working, the entire VR may still appear to be functioning normally during manufacturing and testing, even though the VR may not be able to supply sufficient load current for the information handling system load it is designed to power. In such a case, a defective VR power phase may not be identified during the manufacturing process for an information handling system and may operate properly for powering a lower initial system power load. However, the defective power phase may later cause system malfunction or shut-down in a field installation when additional system power load is added to the system, e.g., during a reconfiguration of the system by a user.
In circuit test (ICT) is a method for testing VR circuitry early during the printed circuit board (PCB) assembly process in an attempt to diagnose circuit failures down to the faulty component pin level. ICT is a method of testing PCB assemblies (PCBAs) that can detect solder shorts and that examines each component on the PCBA individually for correct value and orientation by electrically isolating it from all other components on the board. In order to accomplish this, a “bed-of nails” test fixture is used to provide an interface between every electrical node on the PCBA and the test system voltage source and measurement electronics.
However, current conventional ICT test equipment and procedures cannot identify a bad VR power phase in an example such as described above for several reasons. First, solder joint issues (e.g., such as too much wicking area) cannot be found by ICT because ICT is an electrical test and only optical inspection can find bad solder joints, unless the defect is one that causes shorts to another node or a high impedance (i.e. open) circuit. Second, not all nodes for VR circuitry are verified for open and short circuits by the ICT fixture due to limited access to VR nodes. This is due to issues with impedance loading of the nets by the ICT fixture. Nodal access can also be limited due to space and circuit complexity issues. Third, ICT can simulate proper power sequencing and verify that the output voltage of a VR is correct. However, a bad phase cannot be identified if phase1 in a multi-phase VR is operating normally. In most cases, only phase1 is operating during ICT test for a multiphase VR with auto phase shedding feature since there is no substantial load being applied during the ICT test. As such, other VR phases cannot be validated by ICT. Thus, a defective VR will be incorrectly recognized as operational as long as phase1 is working normally and the value of Vout is within nominal tolerances when measured.